US4713810A - Diagnostic technique for determining fault locations within a digital transmission system - Google Patents
Diagnostic technique for determining fault locations within a digital transmission system Download PDFInfo
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- US4713810A US4713810A US06/777,803 US77780385A US4713810A US 4713810 A US4713810 A US 4713810A US 77780385 A US77780385 A US 77780385A US 4713810 A US4713810 A US 4713810A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/40—Monitoring; Testing of relay systems
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- This invention relates to digital telecommunication systems and more particularly to an in-service line monitoring technique to detect and isolate marginal and failed digital repeatered sections in a digital transmission system.
- This patent application is related to application Ser. No. 777,802, filed Sept. 19, 1985, and is assigned to the same assignee as the present application.
- Digital error detectors spaced along a digital repeatered transmission system, usually detect errors by detecting coding violations in the digital line signal.
- the number of coding violations in any given period of time can be and usually is translated into a bit error rate (BER).
- the BER is a measure of error density, i.e. number of errors/the total number of bits measured. For example, a BER of 1 ⁇ 10 -7 would indicate an error every 10 million bits measured.
- the BER is a very meaningful measure of the performance of a digital transmission system. And, it is an excellent maintenance and diagnostic tool since anything which may affect the quality of the transmitted signal will affect the BER.
- Error detectors monitor the operation of each span in a digital system by checking the BER. Such detectors usually have an internal alarm threshold level setting (often 1 ⁇ 10 -5 or 1 ⁇ 10 -4 ). When this BER is exceeded, an alarm indicative of unacceptable transmission is sent back to a master station over a return path service channel of the transmission system. In fully redundant systems, the alarm signal causes the system to take appropriate action automatically by switching the effected traffic to a spare link or by otherwise removing the failed span from service.
- the present invention provides in-service line monitoring diagnostic technique to detect and isolate marginal and failed digital transmission equipment within a digital telecommunication system having at least two end terminals.
- a digital error detector monitors the bit error rate for each location.
- the detected BER is truncated to include at least the most significant digit and the exponent of the BER.
- the truncated BER is encoded for transmission back to the command center usually located at an end terminal.
- the encoded BER is stored and displayed upon request.
- FIG. 1, comprised of FIGS. 1A and 1B, is a block diagram generally illustrating a digital repeatered transmission system, including a West Terminal (1), intermediate repeater stations (2 and 3) and an East Terminal (4), and more specifically illustrating the service channel and BER detection elements at a master location and a slave location.
- West Terminal 1 consists of a PCM (pulse code modulation) carrier digital multiplexer 5, a digital demultiplexer 6, a digital terminal 7, and a transmitter/receiver microwave radio system 8.
- PCM pulse code modulation
- Digital demultiplexer 6 a digital terminal 7
- transmitter/receiver microwave radio system 8 a microwave radio system
- the instant invention is applicable to any digital transmission system having a bit error rate monitor, and therefore, an optical fiber system could be used, as opposed to the microwave radio link shown (if the appropriate changes were made to the digital transmission carrier (equipment).
- Intermediate repeater stations 2 and 3 may consist of straight through repeaters (as shown in FIG. 1.), drop repeaters, or a terminating office with some through channels to another end office such as East Terminal 4.
- East Terminal 4 is equivalent to the structure shown as West Terminal 1 (except that East Terminal 4 does not have the master BER monitor equipment 30).
- Connecting the two end terminals 1 and 4 with through repeaters 2 and 3 are microwave links 37 and 38, 43 and 44, and 45 and 46. These links and the associated equipment are illustrated and described as single radio channels; however, in practice multiple channels are commonly used with standby channels available for protection purposes (e.g. a 1-for-5 protection system).
- West Terminal 1 accepts a plurality of digital channels (such as T1 line signals) via input paths 31 and conditions the signals for transmission over (W-E) path 37 to intermediate repeater stations 2 and 3.
- West Terminal 1 processes the signals received over (E-W) microwave path 38 and provides a plurality of digital channels on output paths 32 corresponding to the channels on input paths 31.
- the receiver portion of microwave radio 8 demodulates the microwave signals from repeater 2, and separates the service channel signals out on path 51 from the remaining baseband signals applied to path 36.
- the transmitting portion of microwave radio 8 combines the digital baseband signals on path 35 with the outgoing service channel signals on path 52 and modulates the entire band of signals to microwave frequencies for transmission over the microwave path 37.
- the digital terminal equipment 7 provides the basic common digital channel functions for the digital transmission system (such as level coordination, alarm functions, etc.)
- the remaining functions, shown as part of West Terminal 1 consist of the alarm and control functions which are often considered to be, along with the service channel equipment 14, part of the microwave radio interface.
- These error alarm and control functions are provided by the local BER monitor equipment 28, the master BER monitor equipment 30, and the service channel facilities 14 and 15.
- the service channel equipment 14 provides the drop and insert capability to properly interface the order wire, signalling, alarm functions, and user data with the digital baseband signals in the microwave radio 8.
- the input and output connections to the service channel equipment 14 for the bulk of these "ancillary" service channel functions are not shown since these functions, while important transmission system functions, are irrelevant to an understanding of the present invention.
- the service channels signals of interest that is the error alarm and control output signals, appear on path 53 while the input signals are on path 54.
- the program monitor keyboard 19 which is part of the master BER monitor equipment 30, is the command center for the BER monitoring function. More precisely, it provides via path 58 address and command information for the "local" BER monitoring equipment located at each of the repeaters and terminals in the transmission system and for each transmission direction, i.e. E-W and W-E.
- the output signals from program monitor keyboard 19 couple through the service channel interface equipment 15.
- Functionally interface equipment 15 encodes the command signal on path 58 (or decodes the response signal on path 51) from an 8-bit parallel byte into a serial bit stream signal.
- the encoded address and command information to the intermediate stations 2 and 3 is sent, via the service channel facility over paths 54, 52, and 37.
- Program monitor keyboard 19 usually has both a manual mode of operation and an automatic or scan mode. In the scan mode it sequentially addresses each intermediate station and terminal for each direction. When the local BER monitor equipment at an intermediate station or terminal is addressed, the current BER information at that station is encoded and transmitted back to the master station monitor equipment 30 at
- the master BER storage unit 18 is a digital memory unit that holds the latest BER information from each intermediate station and terminal. For multiple radio systems, storage unit 18 stores the BER data for each radio channel and direction as well as for each location. The stored BER data is updated each time a new BER signal is received.
- the master BER access keyboard 20 may be a standard keycircuit electrically connected to the master BER store 18 so that the entry of an appropriate command from the keyboard 20 will cause the current BER information for the selected station, channel, and direction to be visually displayed on the master BER display 21.
- the master BER storage unit 18 may be set up to continuously provide a visual display on the master BER display 21 of the bit error rate from each station, or alternatively, may retain the bit error rate in memory for each station for visual display only on command.
- the BER information is generated by each local BER monitor equipment (shown in FIG. 1 as 28 and 29) and prepared for transmission to the master BER monitor equipment 30.
- the West Terminal 1 is considered to be the master terminal; however, the East Terminal 4 or any intermediate station could also be used as the master terminal.
- the incoming microwave signals appearing on path 37 are received, demodulated, and demultiplexed by microwave radio 9 and then applied to the digital line repeater 10.
- the line repeater 10 regenerates and passes the digital channels on to a East microwave T/R 11 for transmission to a second repeater station 3 and then to East Terminal 4.
- a portion of the digital line signal is applied on path 61 to a standard error detector 22 which computes the BER from the detected data errors.
- the BER number provided by the error detector 22 is a number such as 1.546 ⁇ 10 -7 errors/second. Instead of applying this BER to a threshold detector, as is done in the prior art systems, a truncated version of this number is stored in a buffer register in BER storage 23 for subsequent encoding and transmission to the master BER monitor equipment 30. In the preferred embodiment, the most significant digit (in this example a 1) and the exponent (a-7) are extracted via path 66 and loaded in the local BER storage register 23. When an enable signal from program monitor 19 is received over the service channel facility, it is applied via paths 71 and 70 to an enable input of BER storage 23.
- the service channel interface 25 encodes the digital word representing the most significant digit and the exponent of the BER into a serial data for further processing by the service channel equipment.
- the encoded signal on path 72 is applied through the transmit portion of the service channel signalling equipment 24 to an input of the radio interface 9.
- Radio 9 upconverts the service channel signals and transmits them over the E-W microwave path 38 to the West Terminal 1 where the current BER information is demultiplexed and decoded before being dropped out to master BER store 18, thereby updating the BER information available for that location (repeater 2), channel, and direction. That BER information is stored in the particular register (memory location) for that station, channel and location.
- the local BER information stored in buffer register 23 may be accessed by the local BER access keyboard 26.
- keyboard 26 initiates a transfer causing the data to be displayed on the local BER display unit 27.
- This access capability is useful to maintenance personal wishing to locally check the BER data for a particular channel.
- the BER monitor equipment 29 and 28
- the keyboard 26, display 27, and storage unit 23 could be implement with a personal computer terminal. Since this would be wasteful of its capabilities, a customized dedicated unit would be a preferred structure from an economic standpoint.
- the maintenance technician located at the West Terminal 1 has the capability of periodically monitoring the approximate BER of each link within the system.
- the BER will increase from one span to the next.
- the increase from one span to the next should be gradual and should only change slowly in time.
- the technician can develop a fairly good idea of the performance of the digital system. If however, one span starts to increase with time dramatically, this is an indication that some piece of equipment is perhaps beginning to malfunction. (Microwave path fades can readily be distinguished, by experienced maintenance personnel, from the system malfunctions which would deliteriously affect the BER.
Abstract
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US06/777,803 US4713810A (en) | 1985-09-19 | 1985-09-19 | Diagnostic technique for determining fault locations within a digital transmission system |
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US06/777,803 US4713810A (en) | 1985-09-19 | 1985-09-19 | Diagnostic technique for determining fault locations within a digital transmission system |
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Cited By (32)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4821267A (en) * | 1986-04-11 | 1989-04-11 | Siemens Aktiengesellschaft | Monitoring apparatus for monitoring the operating condition of transmission facilities of communications transmission technology |
US4920537A (en) * | 1988-07-05 | 1990-04-24 | Darling Andrew S | Method and apparatus for non-intrusive bit error rate testing |
US4959849A (en) * | 1989-07-31 | 1990-09-25 | At&T Bell Laboratories | End-to-end network surveillance |
US4970718A (en) * | 1989-03-03 | 1990-11-13 | Digital Equipment Corporation | Apparatus for supplying channel-control signals and maintenance signals in a serial data concentrator system |
US4985894A (en) * | 1987-12-14 | 1991-01-15 | Mitsubishi Denki Kabushiki Kaisha | Fault information collection processing system |
US5031179A (en) * | 1987-11-10 | 1991-07-09 | Canon Kabushiki Kaisha | Data communication apparatus |
US5051740A (en) * | 1989-08-18 | 1991-09-24 | Motorola, Inc. | Paging terminal |
US5090014A (en) * | 1988-03-30 | 1992-02-18 | Digital Equipment Corporation | Identifying likely failure points in a digital data processing system |
US5163051A (en) * | 1990-02-02 | 1992-11-10 | Telecom Analysis Systems Inc. | Paired bit error rate tester |
US5166890A (en) * | 1987-12-15 | 1992-11-24 | Southwestern Telephone Company | Performance monitoring system |
US5191595A (en) * | 1991-04-12 | 1993-03-02 | Telecommunications Techniques Corporation | T1 digital communications system for in-service detection and identification of malfunctioning repeaters |
US5195085A (en) * | 1990-09-11 | 1993-03-16 | At&T Bell Laboratories | Communication link identifier |
DE4309000A1 (en) * | 1992-03-31 | 1993-10-07 | Mitel Corp | Method for determining the reliability of data transmission lines and associated circuitry |
US5299201A (en) * | 1990-09-04 | 1994-03-29 | International Business Machines Corporation | Method and apparatus for isolating faults in a network having serially connected links |
US5408475A (en) * | 1990-06-14 | 1995-04-18 | Motorola, Inc. | Modem with transient impairment detector |
FR2715786A1 (en) * | 1994-02-02 | 1995-08-04 | Trt Telecom Radio Electr | System for transmitting data transmitted by a link comprising intermediate equipment and intermediate equipment for such a system. |
US5448574A (en) * | 1991-02-21 | 1995-09-05 | Nec Corporation | Detection system for abnormal cable connections in communication apparatuses |
US5467341A (en) * | 1994-04-14 | 1995-11-14 | Toshiba America Information Systems, Inc. | Apparatus and method for alerting computer users in a wireless LAN of a service area transition |
US5469463A (en) * | 1988-03-30 | 1995-11-21 | Digital Equipment Corporation | Expert system for identifying likely failure points in a digital data processing system |
US5508941A (en) * | 1991-12-20 | 1996-04-16 | Alcatel N.V. | Network with surveillance sensors and diagnostic system, and method of establishing diagnostics for the network |
US5521907A (en) * | 1995-04-25 | 1996-05-28 | Visual Networks, Inc. | Method and apparatus for non-intrusive measurement of round trip delay in communications networks |
US5600656A (en) * | 1993-06-10 | 1997-02-04 | Siemens Stromberg-Carlson | Remote loopback apparatus and method for telephone line repeaters |
US5726993A (en) * | 1995-10-25 | 1998-03-10 | Siemens Telecom Networks | Signal detector for telephone line repeator remote loopback system |
US5898699A (en) * | 1996-06-28 | 1999-04-27 | Sony Corporation | Digital broadcast receiver and signal level display method |
US6147998A (en) * | 1997-08-26 | 2000-11-14 | Visual Networks Technologies, Inc. | Method and apparatus for performing in-service quality of service testing |
US20020061058A1 (en) * | 2000-07-25 | 2002-05-23 | Symmetricom, Inc. | Subscriber loop repeater loopback for fault isolation |
US6532552B1 (en) * | 1999-09-09 | 2003-03-11 | International Business Machines Corporation | Method and system for performing problem determination procedures in hierarchically organized computer systems |
US6675325B1 (en) * | 1999-10-12 | 2004-01-06 | Lucent Technologies Inc. | Method and apparatus for fault analysis in a communication network |
US7475299B1 (en) * | 2004-02-06 | 2009-01-06 | Cisco Technology Inc. | Method and system for real-time bit error ratio determination |
US7522835B1 (en) * | 2000-04-17 | 2009-04-21 | Ciena Corporation | Method of testing bit error rates for a wavelength division multiplexed optical communication system |
US10997007B2 (en) * | 2019-08-28 | 2021-05-04 | Mellanox Technologies, Ltd. | Failure prediction system and method |
US11171728B2 (en) * | 2011-03-03 | 2021-11-09 | Acacia Communications, Inc. | Fault localization and fiber security in optical transponders |
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Cited By (33)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4821267A (en) * | 1986-04-11 | 1989-04-11 | Siemens Aktiengesellschaft | Monitoring apparatus for monitoring the operating condition of transmission facilities of communications transmission technology |
US5031179A (en) * | 1987-11-10 | 1991-07-09 | Canon Kabushiki Kaisha | Data communication apparatus |
US4985894A (en) * | 1987-12-14 | 1991-01-15 | Mitsubishi Denki Kabushiki Kaisha | Fault information collection processing system |
US5166890A (en) * | 1987-12-15 | 1992-11-24 | Southwestern Telephone Company | Performance monitoring system |
US5090014A (en) * | 1988-03-30 | 1992-02-18 | Digital Equipment Corporation | Identifying likely failure points in a digital data processing system |
US5469463A (en) * | 1988-03-30 | 1995-11-21 | Digital Equipment Corporation | Expert system for identifying likely failure points in a digital data processing system |
US4920537A (en) * | 1988-07-05 | 1990-04-24 | Darling Andrew S | Method and apparatus for non-intrusive bit error rate testing |
US4970718A (en) * | 1989-03-03 | 1990-11-13 | Digital Equipment Corporation | Apparatus for supplying channel-control signals and maintenance signals in a serial data concentrator system |
US4959849A (en) * | 1989-07-31 | 1990-09-25 | At&T Bell Laboratories | End-to-end network surveillance |
US5051740A (en) * | 1989-08-18 | 1991-09-24 | Motorola, Inc. | Paging terminal |
US5163051A (en) * | 1990-02-02 | 1992-11-10 | Telecom Analysis Systems Inc. | Paired bit error rate tester |
US5408475A (en) * | 1990-06-14 | 1995-04-18 | Motorola, Inc. | Modem with transient impairment detector |
US5299201A (en) * | 1990-09-04 | 1994-03-29 | International Business Machines Corporation | Method and apparatus for isolating faults in a network having serially connected links |
US5195085A (en) * | 1990-09-11 | 1993-03-16 | At&T Bell Laboratories | Communication link identifier |
US5448574A (en) * | 1991-02-21 | 1995-09-05 | Nec Corporation | Detection system for abnormal cable connections in communication apparatuses |
US5191595A (en) * | 1991-04-12 | 1993-03-02 | Telecommunications Techniques Corporation | T1 digital communications system for in-service detection and identification of malfunctioning repeaters |
US5508941A (en) * | 1991-12-20 | 1996-04-16 | Alcatel N.V. | Network with surveillance sensors and diagnostic system, and method of establishing diagnostics for the network |
DE4309000A1 (en) * | 1992-03-31 | 1993-10-07 | Mitel Corp | Method for determining the reliability of data transmission lines and associated circuitry |
US5600656A (en) * | 1993-06-10 | 1997-02-04 | Siemens Stromberg-Carlson | Remote loopback apparatus and method for telephone line repeaters |
EP0666660A1 (en) * | 1994-02-02 | 1995-08-09 | T.R.T. Telecommunications Radioelectriques Et Telephoniques | Data transmission system for a link comprising repeaters with an indication of the received signal quality |
FR2715786A1 (en) * | 1994-02-02 | 1995-08-04 | Trt Telecom Radio Electr | System for transmitting data transmitted by a link comprising intermediate equipment and intermediate equipment for such a system. |
US5467341A (en) * | 1994-04-14 | 1995-11-14 | Toshiba America Information Systems, Inc. | Apparatus and method for alerting computer users in a wireless LAN of a service area transition |
US5521907A (en) * | 1995-04-25 | 1996-05-28 | Visual Networks, Inc. | Method and apparatus for non-intrusive measurement of round trip delay in communications networks |
US5726993A (en) * | 1995-10-25 | 1998-03-10 | Siemens Telecom Networks | Signal detector for telephone line repeator remote loopback system |
US5898699A (en) * | 1996-06-28 | 1999-04-27 | Sony Corporation | Digital broadcast receiver and signal level display method |
US6147998A (en) * | 1997-08-26 | 2000-11-14 | Visual Networks Technologies, Inc. | Method and apparatus for performing in-service quality of service testing |
US6532552B1 (en) * | 1999-09-09 | 2003-03-11 | International Business Machines Corporation | Method and system for performing problem determination procedures in hierarchically organized computer systems |
US6675325B1 (en) * | 1999-10-12 | 2004-01-06 | Lucent Technologies Inc. | Method and apparatus for fault analysis in a communication network |
US7522835B1 (en) * | 2000-04-17 | 2009-04-21 | Ciena Corporation | Method of testing bit error rates for a wavelength division multiplexed optical communication system |
US20020061058A1 (en) * | 2000-07-25 | 2002-05-23 | Symmetricom, Inc. | Subscriber loop repeater loopback for fault isolation |
US7475299B1 (en) * | 2004-02-06 | 2009-01-06 | Cisco Technology Inc. | Method and system for real-time bit error ratio determination |
US11171728B2 (en) * | 2011-03-03 | 2021-11-09 | Acacia Communications, Inc. | Fault localization and fiber security in optical transponders |
US10997007B2 (en) * | 2019-08-28 | 2021-05-04 | Mellanox Technologies, Ltd. | Failure prediction system and method |
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